Matt and Kari (above) are correct. There’s a bit of a workaround to get this hourly conversion data, in Google Analytics. I wrote about it here, with instructions. It’s not a perfect fix, but can be very helpful as it shows overall AdWords - only hourly conversion data.

http://dragonsearchmarketing.com/blog/?p=40

It’s no longer possible to find the hourly conversion data within Google Adwords. I think Google decided that this information was a bit too useful for advertisers. Why would they want to show people that their cost per conversion doubled or tripled in the early morning? If they can still make money on you advertising but you don’t make a return, well, that’s your loss. Smart move by them to not provide the information that makes this kind of decision easy.

Anyway, back to the point: when you go to the Report Center in Adwords, when you choose View (Unit of Time) as Hourly (by date) or Hourly (regardless of date), it is impossible to get the conversion data. It is not even an option to display it.

Actually, you can display conversion data hourly, but only if your report type is Pay-Per-Action or Placement Performance. Conveniently enough, both of these report types only show data for the Content Network. Google is trying to hide this information, pure and simple.

Try it yourself to verify. There was also this discussion over a year ago about the fact that this doesn’t work. I guess Google is still trying to fix it

http://www.webmasterworld.com/google_adwords/3253205.htm

Sure, I can explain the hourly reporting feature further. To drill down on your hourly stats, you can choose these reports:
Account Performance
Campaign Performance
Ad Group Performance

And within the View (Unit of Time) selection you can choose from 2 different options to view hourly stats.
I hope this helps!
Thanks!